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NOVEMBER 2018 I PCB007 MAGAZINE 89 By using carefully selected plating condi- tions with correct organic additives types and their concentrations, electrolyte agitation/so- lution flow rates and current density, an ex- cellent void-free through-via-hole filling can be achieved. The process is applicable to ver- tical plating equipment, including VCP. Fur- ther optimization is needed to fill through-via- holes without voids in thicker cores (200 μm). Although the preliminary tests for this case showed promising results, more work is need- ed to confirm and scale up the process. Properties of Plated Copper Coatings Tensile Strength and Elongation Tensile strength and elongation of the plat- ed copper were evaluated per IPC TM-650, Vertical and horizontal pulls were used. Tensile strength >42,000 psi and elon- gation >20% were measured. Tensile strength as a function of the bath age up to 100 AH/L is given in Figure 21, and the elongation results are shown in Figure 22. Plating in a fresh, aged bath met and exceeded IPC specifications. Reliability For TH and via reliability, sections were tak- en, and solder shock resistance testing per IPC TM-650 2.6.8 was performed, with 10-second float at 288°C six times. Tests were run with boards plated in baths with soluble and insol- uble anodes. The holes were examined for any defects. No corner cracks, starter cracks, or TH barrel cracks were present under any plating conditions. Figure 23 refers to TH plating and Figure 24 to via fill. The thermal characteristics of plated copper met the IPC standards and ensured that no fail- Figure 21: Tensile strength versus bath age (AH/L). Figure 22: Elongation, percentage versus bath age (AH/L). Figure 23: Solder dip test for through holes after six times the solder shock (eductor flow and soluble anodes). Figure 24: Solder dip test for blind via after six times the solder shock.

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